(1) Field of the Invention
The present invention relates to a method and apparatus for indicating a speed change operation to be performed for a car having a manual type transmission, especially to an apparatus for indicating or instructing the car driver speed of proper change operations so as to run the car at a shift position, in view of the optimum fuel consumption rate.
(2) Description of Prior Art
With the deterioration of oil supplying situations, various studies have been done for the better utilization of energies or for the improvement of effective utilization of energy sources, such as oil in different industries, of late. In the motor industry as well, various studies on energies having improved thermal efficiencies and a combustion method for better fuel combustion have been carried out and cars having excellent fuel consumption rate performance are now under manufacture.
However, there is a problem in the combustion method according to prior art that unless the driving operation by a driver is good at acceleration manipulation and speed change operations, the improved fuel consumption rate performance cannot be sufficiently realized. As a method for overcoming the problem as described above, it has been proposed that the fuel consumption rates (its unit is g/ps.H) corresponding to the various running conditions of a car are preliminarily measured and stored in a memory as a data map and an optimum shift position of a gear box of transmission is sought, which will take minimum fuel consumption rate in each running condition, and this is indicated to the driver.
Another method has been also proposed heretofore in which a suitable shift position for a more effective and useful fuel consumption rate is sought in accordance with the running conditions of the car and with equal fuel consumption rate characteristic curves obtainable from the engine speed N (rev./min.) versus the ratio between intake air flow Q (1/min.) and engine speed N (rev./min.) as engine load Q/N (1/rev.), where values having equal fuel consumption rate are plotted as shown in FIG. 1 and an optimum speed change operation can be performed by indicating to the driver a suitable shift operation to be performed on display means or by producing a sound through warning means each time speed change becomes necessary.
FIG. 1 shows the equal fuel consumption rate curve graph. In the FIG. 1 supposing that the current fuel consumption rate is at the point J, and one step shift-up operation has been performed from the current shift position, the engine speed N necessary for maintaining the same car speed V (km/H) can be necessarily determined from the transmission gear ratio. As it can be considered that the horse power P (PS) necessary for maintaining the same car speed remains substantially unchanged even if the shift is carried out, the engine load Q/N when performing the one step shift-up operation can be calculated from the characteristic curves. As a result, the new fuel consumption rate after the shift-up operation now moves to the point J', i.e., the fuel consumption rate can be improved in this case. In this case, there is almost no change in the angle of inclination .alpha. formed by the straight line connecting between the points J and J' regardless of the shift-up operation performed in any running conditions, and the angle .alpha. is determined only by the characteristics or the nature of transmission used.
This is also applicable to the case where the shift-down operation is performed from the point K to the point K' in FIG. 1. In such a method described above, however, when the car is running on a slope, e.g., it is running on an ascending slope, a momentary detaching of an accelerator pedal by the driver on the ascending slope makes the engine speed high and puts it in a light load condition. Then, the shift-up indication is displayed on a suitable display, in this case as a result of the determination. On the other hand, when the accelerator pedal is momentarily operated on a descending slope, the engine speed becomes high and it is considered as being in the light load condition so that the similar shift-up indication is carried out.
Accordingly when the shift-up operation is performed on the ascending slope in accordance with the indication thus obtained, the current car speed can be no longer maintained and the car decelerates since the output power is not enough. In this case, however, if the driver operates the accelerator pedal with the shift position as it is, i.e., without change at all, engine vibrations or engine knockings become large an the running becomes difficult.
Similarly, when the shift-up operation is performed on the descending slope in accordance with the indication thus obtained, the acceleration is carried out and there occurs a problem that the engine break can not be effectively operated since the engine speed has been reduced even if the accelerator pedal is released.